The problems posed by substances which deplete the atmospheric ozone layer (ODP: ozone depletion potential) were treated at Montreal, where the protocol imposing a reduction on the production and use of chlorofluorocarbons (CFCs) was signed. This protocol has formed the subject of amendments which have required that CFCs be withdrawn and have extended regulatory control to other products, including hydrochlorofluorocarbons (HCFCs).
The refrigeration industry and that for the production of air conditioning have invested a great deal in the replacement of these refrigerants and thus it is that hydrofluorocarbons (HFCs) have been marketed.
The (hydro)chlorofluorocarbons used as blowing agents or solvents have also been replaced by HFCs.
In the motor vehicle industry, the air conditioning systems for vehicles sold in many countries have changed from a chlorofluorocarbon (CFC-12) refrigerant to a hydrofluorocarbon (1,1,1,2-tetrafluoroethane: HFC-134a) refrigerant which is less harmful to the ozone layer. However, from the viewpoint of the objectives set by the Kyoto protocol, HFC-134a (GWP=1300) is regarded as having a high heating power. The contribution to the greenhouse effect of a refrigerant is quantified by a criterion, the GWP (Global Warming Potential), which epitomizes the heating power, a reference value of 1 being taken for carbon dioxide.
As carbon dioxide is non-toxic and non-flammable and has a very low GWP, it has been proposed as refrigerant for air conditioning systems as a replacement for HFC-134a. However, there are several disadvantages to the use of carbon dioxide, related in particular to the very high pressure of the use thereof as coolant in existing devices and technologies.
The document JP 4110388 describes the use of hydrofluoropropenes of formula C3HmFn, with m and n representing an integer between 1 and 5 inclusive and m+n=6, as heat transfer fluids, in particular tetrafluoropropene and trifluoropropene.
The document WO 2004/037913 discloses the use of compositions comprising at least one fluoroalkene having three or four carbon atoms, in particular pentafluoropropene and tetrafluoropropene, preferably having a GWP at most of 150, as heat transfer fluids.
The document WO 2005/105947 teaches the addition to the tetrafluoropropene, preferably 1,3,3,3-tetrafluoropropene, of a coblowing agent, such as difluoromethane, pentafluoroethane, tetrafluoroethane, difluoroethane, heptafluoropropane, hexafluoropropane, pentafluoropropane, pentafluorobutane, water and carbon dioxide.
The document WO 2006/094303 discloses an azeotropic composition comprising 7.4% by weight of 2,3,3,3-tetrafluoropropene (1234yf) and 92.6% by weight of difluoromethane (HFC-32). This document also discloses an azeotropic composition comprising 91% by weight of 2,3,3,3-tetrafluoropropene and 9% by weight of difluoroethane (HFC-152a).